A proof of the Kim-Vu sandwich conjecture

Fuente: arXiv
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Main Authors: Behague, Natalie, Il'kovič, Daniel, Montgomery, Richard
Format: Preprint
Published: 2025
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author Behague, Natalie
Il'kovič, Daniel
Montgomery, Richard
author_facet Behague, Natalie
Il'kovič, Daniel
Montgomery, Richard
contents In 2004, Kim and Vu conjectured that, when $d=ω(\log n)$, the random $d$-regular graph $G_d(n)$ can be sandwiched with high probability between two random binomial graphs $G(n,p)$ with edge probabilities asymptotically equal to $\frac{d}{n}$. That is, there should exist $p_*=(1-o(1))\frac{d}{n}$, $p^*=(1+o(1))\frac{d}{n}$ and a coupling $(G_*,G,G^*)$ such that $G_*\sim G(n,p_*)$, $G\sim G_d(n)$, $G^*\sim G(n,p^*)$, and $\mathbb{P}(G_*\subset G\subset G^*)=1-o(1)$. Known as the sandwich conjecture, such a coupling is desirable as it would allow properties of the random regular graph to be inferred from those of the more easily studied binomial random graph. The conjecture was recently shown to be true when $d\gg\log^4n$ by Gao, Isaev and McKay. In this paper, we prove the sandwich conjecture in full. We do so by analysing a natural coupling procedure introduced in earlier work by Gao, Isaev and McKay, which had only previously been done when $d\gg n/\sqrt{\log n}$.
format Preprint
id arxiv_https___arxiv_org_abs_2510_20765
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A proof of the Kim-Vu sandwich conjecture
Behague, Natalie
Il'kovič, Daniel
Montgomery, Richard
Combinatorics
In 2004, Kim and Vu conjectured that, when $d=ω(\log n)$, the random $d$-regular graph $G_d(n)$ can be sandwiched with high probability between two random binomial graphs $G(n,p)$ with edge probabilities asymptotically equal to $\frac{d}{n}$. That is, there should exist $p_*=(1-o(1))\frac{d}{n}$, $p^*=(1+o(1))\frac{d}{n}$ and a coupling $(G_*,G,G^*)$ such that $G_*\sim G(n,p_*)$, $G\sim G_d(n)$, $G^*\sim G(n,p^*)$, and $\mathbb{P}(G_*\subset G\subset G^*)=1-o(1)$. Known as the sandwich conjecture, such a coupling is desirable as it would allow properties of the random regular graph to be inferred from those of the more easily studied binomial random graph. The conjecture was recently shown to be true when $d\gg\log^4n$ by Gao, Isaev and McKay. In this paper, we prove the sandwich conjecture in full. We do so by analysing a natural coupling procedure introduced in earlier work by Gao, Isaev and McKay, which had only previously been done when $d\gg n/\sqrt{\log n}$.
title A proof of the Kim-Vu sandwich conjecture
topic Combinatorics
url https://arxiv.org/abs/2510.20765